The present invention relates to improved apparatus for the manufacture of self-locking internally threaded elements and more particularly to a device for the continuous manufacture of elements such as fastners wherein the self-locking feature is obtained through a deformable plastic patch secured onto the threaded internal surface of the element.
In U.S. Pat. No. 3,858,292 entitled "Method of Making Self-Locking Internally Threaded Articles" filed in the name of R.J. Duffy, and assigned to the assignee of the present invention, there is disclosed a method and apparatus for making a self-locking threaded element which avoids the difficulties of resin deposit on the end faces of the threaded element, is effective to deposit resin on the threaded surface in the selected area with a minimum of spatter on other portions of the threaded surface. In that method and device as disclosed, a nut or other internally threaded member was heated, and while mounted with its axis in an up-and-down position was sprayed with finely divided resin particles which were caught and built up on the heated surface to form a plastic body. While the apparatus disclosed in that application has proven quite satisfactory for practicing the method disclosed therein, it has been found that in the mass production of such internally threaded elements, as is desirable for a commercial application of the method, improvements may be made to the apparatus.
For example, automatic means may be provided to continuously move the internally threaded elements through the various stations in which the elements are loaded, the patch is applied to the elements, and the elements are unloaded at a substantial rate. In so doing, it has been found that small amounts of resin material left on the various components of the apparatus is quite detrimental to the elimination of the material deposited on the end surface, or end lead threads of the element. Additionally, in order to insure that the self-locking feature is obtained, the element while being moved through the device in a continuous manner, must be precisely located such that the patch is received at a specific location on the internal threads.
In view of the above therefore, the present invention has as an object to provide an improved device for the manufacture of self-locking internally threaded elements wherein a locking body or patch comprised of resilient thermoplastic material is applied to the element at a precise location, in powdered form.
A further object of the invention is to provide a device for the continuous manufacture of self-locking internally threaded elements which is simple in operation and relatively inexpensive to manufacture and operate.
Still another object of the invention is to provide a device for the manufacture of self-locking internally threaded elements which is automatic, requires little maintenance, is reliable, and is therefore readily adaptable to a manufacturing operation wherein a plurality of such devices may be operated by a single operator.